Although today hydrogen is distributed mainly by trailers, in the long terms pipeline distribution will be more suitable if large amounts of hydrogen are produced on industrial scale. Therefore from the safety point of view it is essential to compare hydrogen pipelines to natural gas pipelines, which arewell established today. Within the paper we compare safety implications in accidental situations. We do not look into technological aspects such as compressors or seals.

Using a CFD (Computational Fluid Dynamics) tool, it is possible to investigate the effects of differentproperties (density, diffusivity, viscosity and flammability limits) of hydrogen and methane on thedispersion process. In addition CFD tools allow studying the influence of different release scenarios, view more

In order for fuel cell vehicles to develop a widespread role in society, it is essential that hydrogen refueling stations become established. For this to happen, there is a need to demonstrate the safety of the refueling stations. The work described in this paper was carried out to provide experimental information on hydrogen outflow, dispersion and explosion behaviour. In the first phase, homogeneous hydrogen-air-mixtures of a known concentration were introduced into an explosion chamber and the resulting flame speed and overpressures were measured. Hydrogen concentration was the dominant factor influencing the flame speed and overpressure. Secondly, high-pressure hydrogen releases were initiated in a storage room to study the accumulation of hydrogen. For a steady release with a view more

This paper shows the experimental results and findings of field explosion tests conducted to obtainfundamental data concerning the explosion of hydrogen-air mixtures. A tent covered with thin plasticsheets was filled with hydrogen/air mixed gas, and subsequently ignited by an electric-spark orexplosives to induce deflagration and/or detonation. Several experiments with different concentrationsand/or volumes of mixture were carried out. The static overpressure of blast waves was measuredusing piezoelectric pressure sensors. The recorded data show that the shape of the pressure-timehistories of the resulting blast waves depends on the difference in the ignition method used. Thepictures of the explosion phenomenon (deflagration and/or detonation) were taken by high-speedcameras.

Large-scale deflagration and detonation experiments of hydrogen and air mixtures provide fundamental dataneeded to address accident scenarios and to help in the evaluation and validation of numerical models.Several different experiments of this type were performed. Measurements included flame front time ofarrival (TOA) using ionization probes, blast pressure, heat flux, high-speed video, standard video, andinfrared video. The large-scale open-space tests used a hemispherical 300-m3 facility that confined themixture within a thin plastic tent that was cut prior to initiating a deflagration. Initial homogeneous hydrogenconcentrations varied from 15%2to 30%2 An array of large cylindrical obstacles was placed within themixture for some experiments to explore turbulent enhancement of the view more

Hydrogen is not more dangerous than current fossil energy carriers, but it behaves differently. Thereforehydrogen specific analyses and countermeasures will be needed to support the development of safe hydrogentechnologies. A systematic step-by-step procedure for the mechanistic analysis of hydrogen behaviour andmitigation in accidents is presented. The procedure can be subdivided into four main parts: 1.) 3D modellingof the H2-air mixture generation, 2.) hazard evaluation for this mixture based on specifically developedcriteria for flammability, flame acceleration and detonation on-set, 3.) numerical simulation of theappropriate combustion regime using verified 3D-CFD codes, and 4.) consequence analysis based on thecalculated pressure and temperature loads.

About 20 years ago Fraunhofer ICT has performed large scale experiments with premixed hydrogenair mixtures [1]. A special feature has been the investigation of the combustion of the mixture withina partial confinement, simulating some sort of a ?lane?, which may exist in reality within a hydrogenproduction or storage plant for example. Essentially three different types of tests have beenperformed: combustion of quiescent mixtures, combustion of mixtures with artificially generatedturbulence by means of a fan and combustion of mixtures with high speed flame jet ignition. Theobserved phenomena will be discussed on the basis of measured turbulence levels, flame speeds, andoverpressures. Conditions for DDT concerning critical turbulence levels and flame speeds as well as ascaling rule for view more

Hydrogen is currently gaining much attention as a possible future substitute for oil in the transport sector.Hydrogen is not a primary energy source but can be produced from other sources of energy. A futurehydrogen economy will need the establishment of new infrastructures for producing, storing, distributing,dispensing and using hydrogen. Hydrogen can be produced in large-scale centralized facilities or in smaller-scale on-site systems. Large-scale production requires distribution in pipelines or trucks. A major challengeis to plan the new infrastructures to approach an even safer society regarding safe use of hydrogen. The paperwill, on the basis of some scenarios for hydrogen deployment, highlight and evaluate safety aspects related tofuture hydrogen economy infrastructures.

Safety is a high priority for a hydrogen refueling station. Here we propose a method to safely refuel a vehicleat optimised speed of filling with minimum information about it. Actually, we identify two major risksduring a vehicle refuelling: over-filling and over-heating. These two risks depend on the temperatureincrease in the tank during refuelling. But the inside temperature is a difficult information to get from thestation point of view. It assumes a temperature sensor in a representative place of the tank and an additionalconnection between the vehicle and the station for data exchange. The refuelling control may not depend onthis parameter only. Therefore, our objective was to effectively control the filling, particularly to avoid thetwo identified risks independently of optional view more

This paper deals with the main safety aspects of the EOS project. The partners of the project ?Politecnico di Torino, Gas Turbine Technologies (GTT, Siemens group), Hysylab (Hydrogen SystemLaboratory) of Environment Park, and Regione Piemonte ? aim to create the main node of a regionalfuel cell generator network. As a first step, the Pennsylvania-based Stationary Fuel Cells division ofSiemens Westinghouse Power Corporation (SWPC) supplied GTT with a CHP 100 kWe SOFC(Solide Oxide Fuel Cell) field unit, fuelled by natural gas with internal reforming. The fuel cell isconnected to the electricity national grid and provides part of the industrial district energyrequirement. The thermal energy from the fuel cells is used for heating and air-conditioning of GTToffices, bringing the total view more

Hydrogen Leaks

Because gaseous hydrogen consists of such a small molecule, very small leaks are common. In properly designed systems these very small leaks do not present a problem as the tiny amount of hydrogen released will not be enough to cause a flammable mixture in air. Only when hydrogen gas can accumulate over time in a confined area will a risk of a flammable mixture or asphyxiation arise.

• Small gaseous hydrogen leaks are difficult to detect by human senses since hydrogen is colorless, odorless, and tasteless.
• If hydrogen accumulates in a confined space in sufficient concentrations it, like all other gasses except oxygen, is an asphyxiant.
• Leaking hydrogen will rise and diffuse quickly in air because its low view more